An independent scientist’s observations on society, technology, energy, science and the environment. “Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.” – Carl Sagan

Posts Tagged ‘energy’

It has been announced this week that the Victorian Government will promote renewable energy by spending $100 million to establish a new regional solar power station, subject to the Federal Government matching its commitment.

Premier John Brumby will announce both initiatives today, focusing on the plan for a 330-gigawatt hours per year solar plant with the capacity to power the equivalent of 50,000 homes.

All right. More kumbaya and rainbows and sunshine courtesy of Brumby.

This proposed new solar power station will supposedly generate 330 gigawatt-hours of electrical energy per year. (The Age article originally mentioned a “330 gigawatt” plant, but they later caught the egregious mistake and edited it.)

How much energy is that?

In 2006, Loy Yang unit A in Victoria generated 15,995 GWh of electrical energy, sent to the grid.
(In doing so, it emitted 19,314,994 tonnes of CO2 equivalent, and a whole lot of other environmentally and aetiologically nasty, dangerous, toxic waste, such as fly ash, SO2 and NO2, as well.) That’s just one example of one of the coal-fired generators, of course.

Therefore, this proposed solar power station is generating about 1.88 percent of that one single coal-fired generating station.

How much will this plant cost? We don’t know. The article doesn’t say, nor does Brumby’s original press release. We don’t know how much it costs, and I doubt Brumby knows, either.

…promote renewable energy by spending $100 million to establish a new regional solar power station, subject to the Federal Government matching its commitment.

OK… we know that it costs at least $200 million. There is actually a convenient benchmark which we can use to make an estimate of how much the whole project will actually cost, and that is the $420 million solar energy installation planned by Solar Systems for northwestern Victoria. This is another expensive solar energy project that the Victorian government just loves to talk about as a poster child for their clean, green ways.

The Solar Systems project, with 154 MW of nameplate capacity, will generate 270 GWh per annum, and will cost 420 million dollars. If we assume that the newly proposed 330 GWh/annum installation might cost about the same, for a given amount of capacity, then we can expect that it will cost 513 million dollars.

To replace Loy Yang A, to have the equivalent amount of energy generation, you’d need 49 such installations of this size, at a cost of approximately 25 billion dollars to construct.

If you build a modern* nuclear power plant, with two 1100 MWe reactors operating with a 90% capacity factor, the plant will generate about 17,356 GWh per annum. That is, such a plant will replace Loy Yang A’s output about 1.09 times over; it’s more than sufficient.

How much does it cost, to build such a nuclear power plant?
Go on, consider an exaggerated, extra-conservative cost estimate from your local greenies. 9 billion dollars? 12 billion? 14 billion? 15 billion?

In every case, even with the most pessimistic cost estimates for nuclear power, it’s far, far cheaper than solar, assuming that you’re actually capable of counting kilowatt-hours.

(* Modern, but not bleeding edge. We’ll consider the presently available modern Generation III LWRs such as Westinghouse AP1000 that are available immediately, not Generation IV fast spectrum reactors, liquid fluoride reactors, or things like that, just to be a little conservative about it.)

Brumby’s press release says that they aim to have the plant operating by 2015. So, they aim to have the plant operating within six years.

Six years? To think that opponents of nuclear energy say that it takes too long to deploy.

If it takes six years to build, and you need 49 of them to replace one coal-fired station, well, would it take 294 years for them to accomplish that goal? Well, perhaps I’m being a tiny bit mendacious. You never know, perhaps they could achieve faster deployment constructing them in parallel, and maybe it would only take 200 years, or 150 years. Maybe.

Six years is in fact sufficient time to construct a nuclear power plant, if you’re serious about doing it and don’t allow it to be delayed. All the nuclear units at the Kashiwazaki-Kariwa nuclear generating station in Japan were each constructed in timescales of between three and five years; Kashiwazaki-Kariwa Unit 2 and Unit 5 both commenced construction in 1985, and both were completed by the end of 1990, within 5 years. Obviously the Japanese operators failed to see any relevance what so ever of a certain ill-fated Soviet graphite pile to their operations.

Even if you want to talk about conservative, drawn out timescales for the construction of new nuclear power in Australia, say, 10 years maybe, it’s still a far, far faster option, for a given amount of energy delivered, than solar or wind.

This is a coal mine. Specifically, it’s the Blair Athol coal mine in central Queensland, Australia, but there’s no special reason why I chose this specific example of a coal mine. The mine produces 12 megatonnes of coal per year. (This is just a satellite image taken from Google Maps, which anybody can of course easily access.)

Coal has a thermal energy content of about 25 MJ/kg, and therefore 12 megatonnes of coal corresponds to a primary energy content of about 2.9 x 1017 J.

This is the Ranger uranium mine, near Jabiru in the Northern Territory of Australia. Again, nothing special about this specific uranium mine, it’s just an example.
All these satellite images are at a consistent scale factor, or zoom level/resolution.

In 2007-2008, Ranger produced 5273 tonnes of U3O8.

A conventional, relatively inefficient low-enriched uranium fuelled LWR with a thermal (primary energy) power output of about 3 GW requires approximately 200 tonnes of U3O8 to be mined to fuel it for one year, assuming that newly mined uranium is used for all its fuel.

Therefore, the annual uranium output from Ranger corresponds to about 2.5 x 1018 J of primary energy, or about 8.6 times the primary energy content supplied by the coal mine.

That is, that one uranium mine supplies the same amount of energy content as nine of the coal mines – one seemingly quite small uranium mine, which is about a third of the size of the coal mine, supplies the same amount of primary energy content as this. (I won’t embed that image in the post, since it will probably completely destroy the formatting of the page.)

The amount of time necessary to exhaust nuclear energy provided by existing uranium deposits, unused energy in current reserves of used radioactive “waste”, heat produced by the radioactive decay of uranium, thorium and potassium deep inside the Earth (in other words, geothermal energy), and uranium in seawater could indeed last billions of years – approaching the evolution of the sun off the main sequence, and with that, the end of life on this world.

If the energy from the Sun is “renewable”, so too is nuclear energy equally every bit as renewable.

The concentration of uranium in seawater in the world ocean is about 3.3 parts per billion. The total mass of Earth’s hydrosphere is about 1.4×1021 kilograms, therefore putting the total mass of uranium in the world ocean at 4.62 billion tonnes.

Current total world demand for electricity stands at 16,330 TWh per year. Let’s conservatively suppose that, over the millennia to come, the average total world demand for electricity is four times what it is at present, or 65,320 TWh. Conventional LEU fueled light-water reactors and inefficient once-through fuel use in these reactors consume about 200 tonnes of uranium mined per gigawatt-year of electric power generation.

Hence, if we make the assumption that all the nuclear energy generation over these coming millenia is performed with this inefficient once-though LEU fuel chain and no recycling or reprocessing of nuclear fuels is performed, then the world demand for uranium can be expected to be 1.49 million tonnes per year.

Hence, consuming 1.49 million tonnes of uranium per year to supply all the world’s electricity, the 4.62 billion tonnes of uranium presently dissolved in the ocean will supply the world’s electricity for 3100 years.

Here we have assumed that no use is made of efficient, advanced reactors or breeder reactors and no use is made of the excess “depleted” uranium-238 or natural thorium, no deuterium is used for nuclear fusion, and no uranium is mined on land. Such assumptions are of course ridiculous, but let’s just be as conservative as possible, for argument’s sake for the purposes of this baseline, worst-case scenario.

If we considered a truly efficient efficient use of nuclear fuel, we may consider an efficient, advanced reactor such as a molten-salt reactor, efficiently transmuting uranium-238 into plutonium-239 in situ to generate energy. We may assume that 200 MeV of energy is released per fission event, and that the efficiency of the 238U transmutation and liberation of useful energy output from these nuclear processes within the reactor is, say, 75% overall. If we assume that this thermal energy is converted in a Brayton-cycle power plant with a thermodynamic efficiency of 50%, then hence we know the amount of natural uranium required to fuel the reactor.

Just over one tonne of natural uranium is required, to generate one gigawatt-year of energy. (That number is basically the same if we’re looking at efficiently burning thorium in a MSR, incidentally, also.) If we utilised nuclear energy efficiently, like this, then the 4.62 billion tonnes of uranium presently dissolved in the ocean would supply the energy we discussed above, 65,320 TWh, for (just under) an astonishing 600,000 years!

However, we are not finished yet. Elution of the uranium in the Earth’s crust into the ocean occurs on an ongoing basis, adding 3.24×104 tonnes of uranium to the ocean annually.

It was motivated by Cohen* that we could recover uranium from seawater at perhaps half of that rate; 16,000 tonnes of uranium from seawater per year. This quantity of uranium would supply 15.4 TW of electric power, if used efficiently as outlined above. In order to supply 65,320 TWh of electricity per year, four times the current worldwide demand for electricity, we only require 7750 tonnes of uranium per year, less than half that figure of 16,000 tonnes.

[* Many of you will be familiar with Cohen’s work, but if you are not, that book is highly recommended.]

Cohen argues that given the geophysical cycles of erosion, subduction and uplift, the uranium elution into the oceans would last for five billion years, at a rate of withdrawal of 6500 tonnes per year. At a rate of consumption of 7750 tonnes per year, in the absence of the use of any uranium and thorium mined on the crust, or the use of deuterium for nuclear fusion, the uranium from the oceans alone can be expected to meet world demand for electricity, at 65,320 TWh of electricity per year, for 4.2 billion years. Over a timeframe on the order of 109 years, of course, some non-trivial fraction will be lost, simply due to radioactive decay – however, at the same time, we have not even begun to consider the use of uranium and thorium reserves in the crust, or the use of the vast supply of deuterium as an energy source.

Clearly nuclear energy remains a viable resource on the Earth for a time scale of approximately five billion years – these nuclear fuels will not be consumed or depleted over a timeframe comparable to the life of the sun on the main sequence. Just as the finite hydrogen within the core of the Sun is a “renewable” energy resource, so too is the finite resource of terrestrial nuclear energy an equally renewable energy resource.

However, there is one final point we have overlooked. Even during its life in the main sequence, the Sun is evolving, as with all such stars. The Sun is gradually increasing in luminosity, by about 10% every one billion years, and its surface temperature is correspondingly slowly rising. This increase in the luminosity of the sun is such that in about one billion years, the surface temperature of the Earth will permanently have become too high for liquid water to exist, the oceans will evaporate and a catastrophe of the most immense proportions imaginable will overtake our planet. The Aztecs foretold a time `when the Earth has become tired… when the seed of Earth has ended’. All life on Earth will be extinguished, billions of years before all the nuclear fuels will be depleted.

In the meantime, our descendants will have evolved into something quite different, as far divergent from us in evolutionary terms as we are from the simplest one-celled organisms to have existed on the Earth. If they still inhabit the Earth, our descendants will leave, perhaps to Mars, or to the moons of the gas giants, Europa, perhaps, rich in water and perhaps not dissimilar to Earth if warmed up a little, or perhaps to a younger, more distant world, orbiting a younger star, around which their civilization will flourish once more.

Now, uranium is technically a finite mineral resource, just like the bauxite used to construct wind turbines is a finite resource and the silica used to construct silicon photovoltaic devices is a finite mineral resource from the Earth.

Five billion or so years from now, the hydrogen within the Sun’s interior will be exhausted, and it will begin to use that in its less dense upper layers. It will expand to eighty times its current diameter, about 7.5 billion years from now, to become a red giant, cooled and dulled as a result of its vastly increased surface area. As the Sun expands, it will swallow up the planet Mercury. However, Earth and Venus can be expected to survive, since the Sun will lose about 28 percent of its mass, and its lower gravity will send them into higher orbits. The Earth will be left scorched, its land surface reduced to the consistency of hot clay by a flux of solar heat a thousand times more powerful than that today, and our atmosphere will be stripped away into space by a now-ferocious solar wind. Not one living cell on this planet will remain alive.

Eventually, the helium produced in hydrogen fusion in the Sun’s outer regions will fall back into the core, increasing the density until it reaches the levels needed to fuse helium into carbon. A “helium flash” will then occur; the Sun will shrink abruptly to slightly larger than its original radius, as its energy source has fallen back to its core. Due to the increase in the reaction rates, due to the increased temperature and pressure at the stellar core, and the smaller amount of helium compared to hydrogen, the complete helium-burning stage will last only 100 million years. Eventually it will have to again resort to its reserves in its outer layers, and will again attain a red giant form. This phase lasts a further 100 million years, after which, over the course of a further 100,000 years, the Sun’s outer layers will fall away, ejecting a vast stream of matter into space and forming a planetary nebula.

Eventually, all that will remain of the Sun is a white dwarf, a hot, dim and extraordinarily dense object; half its original mass but only the size of the Earth. Were it viewed from Earth’s surface, it would be a point of light the size of Venus with 100 times its current apparent luminosity. Eventually, after trillions of years, it will fade and die, finally ceasing to shine altogether.

Why is geothermal energy produced by the of uranium in the ground considered as “renewable” when that produced by fissioning those same atoms in a reactor is not?

The answer, of course, is that that’s not the point. The point is that “renewable”, as we hear the term used in society today, doesn’t have any rigorous physical meaning. Loosely, the popular definition of “renewable” means “not fossil fuels and not nuclear energy”, and fossil fuels do not meet the above definition when used at today’s consumption rates (if oil use were cut by a factor of 100,000, it would also be renewable). More correctly, “renewable” energy has come to refer to anything that the Green lobby hasn’t chosen to oppose – anything except fossil fuels or nuclear reactor-derived energy. (Nuclear geothermal energy seems to be OK, though.)

When something does meet the definition that the environmentalist lobby doesn’t like, they amend the mysterious unwritten non-scientific definition to exclude it.

For example, whale oil could produced by farming whales, constituting “renewable biofuel”, in exactly the same way that sugarcane-derived ethanol is in principle a “renewable” fuel. I can’t see the capital-G Green lobby being too keen about the idea, though.

Now, it seems reasonable to argue that, for example, wind energy or solar energy are not in fact consuming any significant finite resources at all during their ongoing operation, the raw materials such as aluminium, silicon or concrete used in the construction of their infrastructure not withstanding.

Opponents of nuclear energy often seem keen to point out that nuclear fuels are what they often describe as “finite, nonrenewable” resources. However, there’s no such thing as a source of energy that we can use without consuming any finite resource, because the energy that we can extract from any isolated system is in itself a finite resource. When the free energy of the universe is expended, the “heat death” of the entire universe is the result. This is the end of all that is, all that was, and all that ever will be, and this is going to happen.

There’s no such thing as “renewable energy”.

The free energy of any isolated system, for any reasonably literal, sensible definition of the word renewable, is not “renewable”.

“Renewable energy” does not exist. That’s the second law of thermodynamics.

I’ve been looking at some of the claims on the website of Thermogen recently.

In short, what Thermogen claim is that they can supply a domestic solar thermal energy installation whch provides an electrical power output of 5 kWe, and that that power output is accessible 24 hours a day via energy storage in tanks of high-temperature water.

The Thermogen is designed to supply it’s rated output 24 hours per day, cloudy or sunny weather e.g. a 5kW system will supply 120kW per day. [sic] It has a three day design storage for inclement weather.

Of course, if a 5 kW system can supply 5 kW of power for 24 hours, then that’s 120 kilowatt-hours of energy. I’m a little bit wary of a company selling energy technology when they can’t tell the difference between a unit of energy and a unit of power.

This heated water is then stored in 1000 litre insulated tanks at 150-200 °C. These tanks are a solar energy storage system designed to store enough energy to provide the following services for up to three days without sunshine:

For a 5 kWth system to be able to store energy up for three days, then 360 kWhth of energy must be stored in the system. We’ll come back to that in a minute.

They explain that:

Each panel measures 2.4m wide and 2m up the roof. It is expected that you will need 7 of these panels for the Thermogen system.

That’s a collector area of 33.6 m2. A little less than that, actually, since not 100% of the panel’s dimensions will be usable solar collector area.

For comparison, a standard large two-panel Solahart hot-water system has a collector area of 3.5 square metres.

If there is one idea to keep in mind when considering solar energy, that is it. Irrespective of what sort of collector technology you have, there is always a very finite limit to the amount of energy you can collect from a solar collector of a given area. That energy flux is the maximum that there is to be utilised, no matter what technology you use to harvest it.

So, anyhow, we have 21 MJ/m2/day, and a rooftop solar collector of 33.6 m2. We’ll be conservative here and assume (a) you live in Townsville or Alice Springs or Darwin and (b) the entirety of the surface area of those collectors is active area. So, the power output that you get is a maximum of 705.6 megajoules per day.

The most efficient evacuated-tube solar thermal energy collectors, like the ones proposed by Thermogen, manage a gross efficiency of energy collection of about 60%. So, now we’re down to 423.36 MJ per day.

This thermal energy is then converted into electrical energy in a heat engine. In this case, the engine that they’ve pictured on their webpage – without attributing it’s source – is a Freepower 6 [PDF link] 6 MWe Organic Rankine Cycle powerplant.

Some of the images on the Thermogen site appear to depict the FreePower 6 organic Rankine cycle engine / generator as well as a Rotartica absorption chiller, with no credit given to the peope responsible for these components.

(An organic Rankine cycle is simply a Rankine cycle engine using an organic chemical as the engine’s working fluid, such as a fluorocarbon liquid, a fluorocarbon gas like a refrigerant type material, or some type of liquid with a lower boiling point than water, as the engine’s working fluid. Such engines are commonly used to recover low-grade heat from industrial processes, and as geothermal electricity generators, since they’re designed to operate with low temperatures.)

Now, let’s look at the specs of the FreePower 6 engine. It requires a heat source of 180 °C, returns the cooled oil at 123 °C, and requires a thermal power input of 70 kWth, to generate an electrical power output of 6 kWe. Since the Thermogen system is supposed to generate 5 kWe, I presume 1 kWe is consumed to drive the hot water pumps.

Therefore, the engine only has an efficiency of 8.6% – seemingly very low efficiency indeed. That seems like a terribly low efficiency, but the maximum efficiency – as per Carnot’s theorem – at these temperatures is only 11.6%, so the efficiency realised in practice isn’t too bad. At least these guys aren’t trying to flog off a perpetual motion machine.

Now, if we’re putting 423.36 MJ into the engine, and our electricity output is uniform day and night, then at this efficiency, we have a thermal input power of 4.9 kW, and we’re getting an electrical power output of 421.4 Watts.

I suppose that might be where they’re getting their claimed of “5 kW” from, given that they’re putting an average power of about 5 kW thermal into the engine?

Furthermore, cooling water is required to dissipate the engine’s 60 kWth of waste heat, at a flow rate of up to about 0.8 L/s and a maximum outlet temperature of 55 °C. I’m afraid that yes, in this house, we obey the laws of thermodynamics. Perhaps you need to build an artificial pond next to it or something? But that’s good, right? Lake Anna attracts lots of tourists, doesn’t it? 😉

If you have a small household, or an energy-efficient household, then such an installation can realistically meet all your household electricity needs. Probably. If you live in northern Australia. If you live in Melbourne, Sydney or Adelaide, forget about it. Even if you could supply all household demand for electricity, however, there will be little or none left to sell into the grid.

They claim that the power generated from a domestic Thermogen installation “will supply a revenue stream of up to $20,000 per annum at current rates which will pay the mortgage on most homes in Australia”.

It won’t.

If we really did want to generate 120 kWh of electricity per day, what would be required? You’d simply need 400 square meters of collector panels. That won’t fit on your roof. It would be the kind of system that lives up to what they’re claiming, though.

This is before we even start thinking about the energy storage tanks of a couple of thousand litres of water at 150 to 250 °C – superheated water at pressures exceeding 200 psi. If you’re standing around the tank and it ruptures, it will cook you to death. Do you really want this engineered and installed in homes by people who can’t tell the difference between power and energy?

For a 5 kW system to be able to store energy up for three days, then 360 kWh of energy must be stored in the system.

If the initial temperature of the water is 180 °C, and the final temperature of the water is 123 °C, then the storage of 360 kWhth to supply three days worth of energy requires 360 kWh / (4.184 Jg-1K-1 * 57 K * 1 g cm-3) = 5434 L; 6 quite large 1000 L storage tanks.

How much does all this cost, anyway? There is not one word of it on the site thus far.

There’s nothing especially malicious or ill-intentioned about Thermogen – although I would not invest in them under any circumstances. They simply appear to be another trendy, hopeful “Green” enterprise that simply can’t count.

There is an interesting little thread over at the The Oil Drum discussing gas turbines for nuclear energy systems, and the engineering challenges associated with the same, for example the pros and cons of different gases which may be used.

Given that Brayton-cycle powerplants are certain to play an important part of the development of modern nuclear energy technology, (irrespective of whether you’re interested in LFTRs or PBMRs or any one of a dozen different types of reactor technology, they can all usefully be combined with gas turbine energy conversion) it’s a very interesting area to keep abreast of.

There’s also another, longer, more heated recent thread debating nuclear energy in general on TOD, which started off as a post on seawater uranium, which has degenerated a little bit into a familiar Sisyphean argument about nuclear power, but it’s there all the same, if you want to have a look.

But could nuclear power really “kill the coal industry” in Australia? I don’t think so.

Total production of raw black coal in Australia in 2006 was 405 Mt (million tonnes). This production represented a small increase of 1.6% over the 2005 figure of 399 Mt. After processing, a total of 317 Mt of metallurgical and thermal black coal were available for both domestic use and export in 2006.
(I’ve taken these statistics from the Australian Coal Association website.)

In 2006, Australia’s domestic consumption of black coal for electricity generation amounted to 62.4 million tonnes of black coal. Hence, domestic electricity generators consume only about 20% of Australia’s output of processed black coal. Other domestic industrial uses of coal, such as steel production, account for about three percent, with the entire remaining 77% being exported.

(The ACA’s statistics refer exclusively to black coal – however, brown coal is a much smaller resource, relatively, and since we have the statistics for black coal, I’ll limit the discussion to black coal.)

Hence, under the worst case scenario (or best case scenario), we may envisage a future in which every coal-fired generator in Australia is closed down and replaced by nuclear power plants. This would result in cutting Australia’s greenhouse gas emissions in half – at the cost of a 20% reduction in coal demand. If we were to see half of Australia’s coal fired plants closed down and replaced by nuclear energy, we will see a 10% reduction in coal revenue.

I don’t think a 10% to 20% downturn in revenue constitutes “killing the coal industry” – and I really don’t think that the coal industry has anything to worry about for the foreseeable future.